Solid electrolyte and preparation method thereof, and electrochemical device and electronic device comprising solid electrolyte

Abstract

Embodiments of the present application relate to a solid electrolyte and a preparation method thereof, and an electrochemical device and an electronic device comprising the solid electrolyte. The solid electrolyte comprises a lithium-containing transition metal sulfide being represented by the chemical formula of Li2−2a+bCd1+aMcGe1−dS4, where M is selected from the group consisting of Al, Ga, In, Si, Sn and a combination thereof, wherein 0<a≤0.25, 0≤b≤0.2, 0≤c≤0.2, and 0≤d≤0.2. The embodiments of the present application effectively improve the shortcomings of poor chemical stability of the conventional thiophosphate solid electrolyte in an atmospheric environment by providing the above solid electrolyte having a thio-LISICON structure and containing no phosphorus (P), so that the solid electrolyte has both good chemical stability and high ionic conductivity, thereby reducing the processing environment requirements and manufacturing cost of the solid electrolyte.

What is claimed is: 
     
       1. A solid electrolyte, comprising a lithium-containing transition metal sulfide being represented by the chemical formula of Li 2−2a+b Cd 1+a M c Ge 1−d S 4 , wherein a=0.25, 0≤b≤0.2, 0<c≤0.2, 0≤d≤0.2 and M is selected from the group consisting of Al, Ga, In, Si, Sn and a combination thereof. 
     
     
       2. The solid electrolyte according to  claim 1 , wherein the lithium-containing transition metal sulfide belongs to an orthorhombic system and has a thio-LISICON crystal structure, and the basic constituent unit of the thio-LISICON crystal structure comprises tetrahedral structural units of LiS 4 , CdS 4 , MS 4  and GeS 4 . 
     
     
       3. The solid electrolyte according to  claim 1 , further comprising a binder and a lithium salt, wherein the binder is selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate ester, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber and a combination thereof, and the lithium salt is selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO 2 CF 3 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalate)borate (LiBOB), lithium difluoroborate (LiF 2 OB) and a combination thereof. 
     
     
       4. The solid electrolyte according to  claim 1 , wherein the ionic conductivity of the lithium-containing transition metal sulfide is 10 −6  S/cm to 10 −4  S/cm with a variance of ±10% of the numerical value. 
     
     
       5. A method for preparing a solid electrolyte, comprising:
 mixing a Li-containing material, a Cd-containing material, an M-containing material, a Ge-containing material and an S-containing material according to a stoichiometric ratio of Li 2−2a+b Cd 1+a M c Ge 1−d S 4 , to form a mixture, wherein M is selected from the group consisting of Al, Ga In, Si, Sn and a combination thereof, wherein a=0.25, 0≤b≤0.2, 0<c≤0.2, and 0≤d≤0.2; 
 heating the mixture to a solid phase reaction critical temperature, and then cooling to room temperature to obtain a lithium-containing transition metal sulfide; and 
 forming the solid electrolyte using the lithium-containing transition metal sulfide. 
 
     
     
       6. The method according to  claim 5 , wherein the step of heating the mixture to a solid phase reaction critical temperature comprises heating the mixture to 600° C. to 1000° C. with a variance of ±10% of the numerical value. 
     
     
       7. The method according to  claim 5 , wherein the step of forming the solid electrolyte using the lithium-containing transition metal sulfide comprises:
 placing the lithium-containing transition metal sulfide in a cold pressing mold; and 
 cold-pressing the lithium-containing transition metal sulfide to form the solid electrolyte. 
 
     
     
       8. The method according to  claim 5 , wherein the step of forming the solid electrolyte using the lithium-containing transition metal sulfide comprises:
 adding a binder into a solvent to prepare a solution, wherein the binder is selected from the group consisting of polyvinylidene fluoride, a vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate ester, polyacrylic acid, polyacrylate salt, sodium carboxymethyl 
 cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber and a combination thereof; 
 adding the lithium-containing transition metal sulfide and a lithium salt into the solution, and stirring uniformly to form mixed slurry, wherein the lithium salt is selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO 2 CF 3 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalate)borate (LiBOB), lithium difluoroborate (LiF 2 OB) and a combination thereof; and 
 applying the mixed slurry onto a substrate, and then drying the mixed slurry to form the solid electrolyte. 
 
     
     
       9. An electrochemical device, comprising:
 a cathode; 
 an anode; and 
 a solid electrolyte, wherein the solid electrolyte comprises a lithium-containing transition metal sulfide being represented by the chemical formula of Li 2−2a+b Cd 1+a M c Ge 1−d S 4 , wherein a=0.25, 0≤b≤0.2, 0<c≤0.2, 0≤d≤0.2 and M is selected from the group consisting of Al, Ga, In, Si, Sn and a combination thereof. 
 
     
     
       10. The electrochemical device according to  claim 9 , wherein the lithium-containing transition metal sulfide belongs to an orthorhombic system and has a thio-LISICON crystal structure, and the basic constituent unit of the thio-LISICON crystal structure comprises tetrahedral structural units of LiS 4 , CdS 4 , MS 4  and GeS 4 . 
     
     
       11. The electrochemical device according to  claim 9 , wherein the solid electrolyte further comprises a binder and a lithium salt, wherein the binder is selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate ester, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber and a combination thereof, and the lithium salt is selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO 2 CF 3 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalate)borate (LiBOB), lithium difluoroborate (LiF 2 OB) and a combination thereof. 
     
     
       12. The electrochemical device according to  claim 9 , wherein the ionic conductivity of the lithium-containing transition metal sulfide is 10 −6  S/cm to 10 −4  S/cm with a variance of ±10% of the numerical value. 
     
     
       13. An electronic device, comprising an electrochemical device, wherein the electrochemical device comprises:
 a cathode; 
 an anode; and 
 a solid electrolyte, wherein the solid electrolyte comprises a lithium-containing transition metal sulfide being represented by the chemical formula of Li 2−2a+b Cd 1+a M c Ge 1−d S 4 , wherein a=0.25, 0≤b≤0.2, 0<c≤0.2, 0≤d≤0.2 and M is selected from the group consisting of Al, Ga, In, Si, Sn and a combination thereof. 
 
     
     
       14. The electronic device according to  claim 13 , wherein the lithium-containing transition metal sulfide belongs to an orthorhombic system and has a thio-LISICON crystal structure, and the basic constituent unit of the thio-LISICON crystal structure comprises tetrahedral structural units of LiS 4 , CdS 4 , MS 4  and GeS 4 . 
     
     
       15. The electronic device according to  claim 13 , wherein the solid electrolyte further comprises a binder and a lithium salt, wherein the binder is selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate ester, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber and a combination thereof, and the lithium salt is selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO 2 CF 3 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalate)borate (LiBOB), lithium difluoroborate (LiF 2 OB) and a combination thereof. 
     
     
       16. The electronic device according to  claim 13 , wherein the ionic conductivity of the lithium-containing transition metal sulfide is 10 −6  S/cm to 10 −4  S/cm with a variance of ±10% of the numerical value. 
     
     
       17. A solid electrolyte, comprising a lithium-containing transition metal sulfide being represented by the chemical formula of Li 2−2a+b Cd 1+a M c Ge 1−d S 4 , wherein a=0.25, 0≤b≤0.2, 0<c≤0.2, 0≤d≤0.2 and M is selected from the group consisting of In, Si, and a combination thereof. 
     
     
       18. The solid electrolyte according to  claim 17 , wherein the lithium-containing transition metal sulfide belongs to an orthorhombic system and has a thio-LISICON crystal structure, and the basic constituent unit of the thio-LISICON crystal structure comprises tetrahedral structural units of LiS 4 , CdS 4 , MS 4  and GeS 4 . 
     
     
       19. The solid electrolyte according to  claim 17 , further comprising a binder and a lithium salt, wherein the binder is selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate ester, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber and a combination thereof, and the lithium salt is selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO 2 CF 3 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(SO 2 CF 3 ) 3 ), lithium hexafluorosilicate (LiSiF 6 ), lithium bis(oxalate)borate (LiBOB), lithium difluoroborate (LiF 2 OB) and a combination thereof. 
     
     
       20. The solid electrolyte according to  claim 17 , wherein the ionic conductivity of the lithium-containing transition metal sulfide is  10   −6  S/cm to  10   −4  S/cm with a variance of ±10% of the numerical value.